Ford Focus ST Mk3 (ST250) Tuning Guide

Ford Focus ST Mk3 ST250 Tuning Guide

The Ford Focus ST Mk3 ST250, spanning from 2012 to 2018, is a popular performance car that offers a strong balance between everyday usability and thrilling driving experience. Whether you own a pre-facelift model (2012-2014) or the facelift model (2015-2018), tuning the ST250 to unlock more performance potential is a common desire. However, understanding the right approach to tuning is key to maintaining reliability and maximising the car's capabilities.

This guide covers the primary areas for tuning, recommended modifications, and the power limits of the engine to help you make informed decisions. If you are seeking the very best performance parts for your ST250 - check out our dedicated page here!

Power Limits and Engine Considerations

The stock 2.0-litre turbocharged engine in the ST250 produces around 247bhp and 360Nm of torque, which is already a strong output for a hot hatch. However, enthusiasts looking to increase performance often aim for figures upwards of 300bhp.

It’s important to note that the engine has an approximate safe power limit of 315-320bhp. Pushing beyond this figure on a standard engine is possible, but it is not recommended without upgrading critical components. The standard engine internals, while robust, may not reliably handle significantly more power, especially if the car is driven hard or frequently on track.

To increase power safely beyond 320bhp, it’s highly recommended to upgrade the engine internals. Key upgrades include:

• Forged Pistons and Rods: These stronger components are designed to withstand higher levels of pressure and heat generated at elevated power levels. They are a critical upgrade when pushing the engine beyond 320bhp. JXL Performance recommends Mahle Motorsport Pistons and BW H-Beam Connecting Rods
• Forged Bearings: Upgrading the bearings ensures the engine can handle higher stresses from increased power without risking premature failure. JXL Performance recommends King Race Bearings, or ACL Race Main Bearings
• Head Studs/Main Studs: Stronger head and main studs help keep the engine block and cylinder head securely fastened, reducing the risk of head gasket failure, which can occur when pushing more power through a stock engine. JXL Performance recommends ARP for all stud needs

These upgrades, while adding to the cost and complexity of the build, will allow you to safely run higher power figures and improve the longevity of the engine under heavy load. Check out our full range of engine build parts here.

Stage 1: Basic Power Gains

For those looking for a relatively straightforward performance increase, Stage 1 tuning is a good place to start. This typically involves an ECU remap to optimise the engine’s performance. A Stage 1 remap can increase power to around 280bhp, depending on the exact parameters and the quality of the remap.

A Stage 1 upgrade typically requires no other hardware changes, making it the most cost-effective and simple way to boost performance. The remap improves throttle response, optimises air-fuel ratios, and increases boost pressure, giving noticeable power gains and a more engaging driving experience.

Stage 2: More Power and Hardware Upgrades

At Stage 2, the focus shifts from purely software tuning to hardware improvements. To handle the increased power and ensure the car remains reliable, several components need upgrading.

• Upgraded Intercooler: A larger or more efficient intercooler helps cool the intake air, improving performance and reducing the risk of heat soak. This is a common upgrade at Stage 2. JXL Performance recommends AIRTEC Motorsport Stage 2 Intercooler Upgrade
• Induction Kit: A high-flow induction kit allows for improved airflow into the engine, increasing the engine’s efficiency and power output. JXL Performance recommends AIRTEC Motorsport Stage 2 Induction Kit
• Downpipe/Exhaust: A high-flow downpipe and cat-back exhaust are required for maximum gains. A sports-cat will remain legal for MOT purposes in the UK, whereas a de-cat downpipe is for off-road use only. For readers in Europe you will need to seek a CE marked, or TUV approved unit dependent on your region and local requirements. JXL Performance recommends Milltek Sport Exhausts for your Focus ST250
• Stage 2 ECU Remap: Alongside hardware upgrades, a Stage 2 remap optimises the engine’s new parameters, helping you achieve a power figure between 300-320bhp.

A Stage 2 setup can deliver a significant increase in performance and responsiveness, while still keeping the car within the limits of a stock engine, as long as you do not exceed 320bhp. 

Stage 3: Comprehensive Upgrades for Maximum Power

For those who want to push their Focus ST Mk3 to its maximum potential, Stage 3 tuning represents the most comprehensive and high-performance setup. Stage 3 involves significant engine and hardware upgrades to handle the increased power.

• Upgraded Turbocharger: At Stage 3, upgrading to a larger or hybrid turbocharger is necessary to increase airflow and boost pressure. This provides the biggest gains in power and performance. Power can rise up to and above 500bhp dependent on your chosen turbo and supporting hardware/software
• Upgraded Fuel System: A larger fuel pump and high-flow fuel injectors ensure that the engine receives enough fuel to support the increased power levels.
  
• Stage 3 ECU Remap: With all the hardware changes in place, a Stage 3 remap finalises the tuning, ensuring that all components work together efficiently and safely. At this stage, you can see power figures between 350-400bhp, depending on the quality of the turbo upgrade and the supporting modifications.
• Engine Building: At Stage 3 power levels, you are in excess of what is recommended to be running on a standard engine. Consider upgrading your internal engine parts with forged pistons, forged connecting roads, performance bearings and stronger head and main studs. 

Boosting Issues and Reliability Considerations

Before embarking on any significant tuning, it’s important to address potential issues that could arise with the Focus ST Mk3. One common issue in turbocharged engines is boost leaks, which can affect performance and power delivery.

• MAP Sensor: The MAP sensor is responsible for measuring the air pressure in the intake manifold. A faulty sensor can cause incorrect readings, leading to poor performance.
• MAF Sensor: The MAF sensor measures the amount of air entering the engine. If this sensor is faulty, the engine may not run as efficiently, impacting performance.
• Boost Solenoid: The boost solenoid controls the boost pressure. A malfunction here can result in inconsistent or reduced boost levels, leading to a loss of power.

If you experience any performance issues, it's worth checking these sensors. If the problem persists, using diagnostic tools such as Forscan can help pinpoint the issue and allow for further investigation.

Conclusion

Tuning the Ford Focus ST Mk3 ST250 can unlock significant performance gains, but it's important to approach it with careful consideration. For those looking to push beyond the stock power, upgrading the engine internals with forged pistons, rods, bearings, and head studs is crucial for reliability and longevity. Stages 1 and 2 tuning offer solid power increases, while Stage 3 provides a comprehensive setup for those looking for maximum power.

By following the recommended upgrades and ensuring your engine can handle the extra load, your Focus ST Mk3 ST250 can deliver an exciting and reliable driving experience well beyond its factory capabilities. Always ensure that any tuning is done with proper planning, and take care to address any potential reliability issues to keep your car performing at its best.